Spiny head sida
- Considered to be from tropical America, this weed invades disturbed and overgrazed areas.
- An erect small shrub growing to around 1.5 m.
- Stems woody, branching several times, with well-developed tap root.
- Leaves narrow, lance shaped, tapered both ends, serrated edges.
- Yellow flowers, usually solitary or in pairs in the leaf axils.
- Fruit is a hard, dark brown dry capsule, splitting into 5-8 segments each with a wedge-shaped, black seed having 2 sharp points at one end.